In recent years, gas-liquid mixture fluid containing micro bubbles is used in various industries, such as, for dissolution of a dysoxic water mass in a closed water area, an activation means of microorganisms in drainage treatment, growth facilitation of plants in hydroponics and the like, and removal of contaminating substances on a substance surface, as a technique capable of supplying various gases into water by making such gases in the form of micro bubbles.
For example, in Japanese Unexamined Patent Application No. 2003-182158, a spare swirl portion is provided in order to rectify a liquid introduced from a liquid introduction opening into a gas-liquid swirl chamber, and a swirl flow is generated to a wall surface in which a gas introduction opening is provided, the wall surface being orthogonal to a surface in which the liquid introduction opening is arranged. While generating the swirl flow, the liquid turns backward at the wall surface in which the gas introduction opening is provided, and a gas is drawn by utilizing negative pressure of the swirl flow and discharged to a discharge opening toward an opposite wall surface in which the discharge opening is provided.
In Japanese Unexamined Patent Application No. 2008-272719, a plurality of annular grooves is provided in such a manner that gas-liquid mixture fluid introduced into a gas-liquid swirl chamber is not expanded in the axial direction, and a swirl flow of the gas-liquid mixture fluid is generated to a wall surface in which a gas-liquid mixture fluid introduction opening is not provided, the wall surface being orthogonal to a surface in which the gas-liquid mixture fluid introduction opening is arranged. The gas-liquid mixture fluid turns backward at the wall surface, goes toward an opposite wall surface in which a discharge opening is provided while increasing swirl speed, and is discharged to the discharge opening.